The objective of this application is to link language-learning difficulties seen in two populations: children with Specific Language Impairment (SLI) and adults learning a second language (L2). Through the applicant's research on typical language development, she has developed a novel perspective about what makes infants precocious language learners, which she is using to make novel predictions about learning difficulties in childhood SLI and adult L2 learning. The applicant's current work with LouAnn Gerken (Quam, Knight, & Gerken, under review) and other evidence suggests that infants are surprisingly willing to attend to new acoustic dimensions in word learning. She proposes that this open-mindedness might make infants particularly good at learning new linguistic structure (see also Newport, 1991). She has identified two factors that seem to contribute to open-mindedness: slow development of explicit-learning mechanisms (Jones & Herbert, 2006; Richmond & Nelson, 2007)-which biases infants to rely on implicit learning-and limited knowledge of which dimensions are relevant for differentiating sounds in the native language. These insights have important implications for two groups who struggle to learn new linguistic structure: adult L2 learners and children with SLI. For adult L2 learners, we predict that blocking access to both explicit learning and native-language biases will facilitate learning of L2 categories. For typically developing 4- and 5-year-olds learning artificial sound categories, we predict a similar result. Both groups have intact implicit-learning abilities which are often overshadowed by their strong explicit skills, so blocking access to explicit skills should facilitae their implicit learning. However, predictions diverge for children with SLI, who have been argued to have weak implicit- learning skills (Lum, Conti-Ramsden, Page, & Ullman, 2011). Thus, these children should struggle to learn categories that are best learned implicitly. The mentored-phase training in language disorders at the University of Arizona will capitalize on an existing collaborative relationship between mentor Dr. Elena Plante (Speech, Language and Hearing Sciences; SLHS) and co-mentor Dr. LouAnn Gerken (Psychology) to provide the applicant with coursework and research skills pertinent to SLI. The mentored research will be advised by a team of mentors and advisors with the requisite expertise to train the applicant in SLI (Dr. Plante), connections between typical development and SLI (Drs. Gerken and Plante) implicit/explicit category learning (Dr. Todd Maddox, UT Austin), and language-specific skills and biases in sound-category learning (Dr. Lotto).